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Electronics Manufacturing Processes Manufacture of Electronics Components Manufacture of Printed Circuit Boards (PCB’s) Assembly of components on PCB’s Electronics Manufacturing Processes Manufacture of Electronics Components Manufacture of Printed Circuit Boards (PCB’s)

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Electronics Manufacturing Processes

Manufacture of Electronics Components

Manufacture of Printed Circuit Boards (PCB’s)

Assembly of components on PCB’s


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Electronics Manufacturing Processes

Manufacture of Electronics Components

Manufacture of Printed Circuit Boards (PCB’s)

Assembly of components on PCB’s


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Electronics Component Manufacture

Electronics Components

Mechanical and Electro-mechanical:

PCB mounted DIP switches, mains switches, disc drives

Passive Solid State Devices:

Resistors, Capacitors

Active Solid State Devices:

Transistors, Diodes, Thermionic valves, FETs and MOSFETs


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Passive devices: resistors

Carbon Composite Resistor

Slug  leads  mold  bake  seal

- cheap, poor tolerance, rugged

Wire-wound resistor

wind wire  leads  mold  seal

- high power, low resistance, high frequency apps

Film resistor

Film is cut by laser  high precision

- low frequency applications


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Passive devices: capacitors

Tabbed tubular paper capacitor

Tubular ceramic capacitors

Disk-ceramic capacitor


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Active devices: Silicon wafer production

Raw Si:

Quartzite (SiO2) + Carbon (C) + Heat + catalysts  Si + CO2

Pure Si:

Si + HCl  SiCl4 + Hydrogen  Fractional distillation 

SiCl4 + H2 + catalysts  Si + HCl

Pure Monocrystalline Si:

Melt pure Si, Seed crystal drawn out slowly

Typical Single Crystal Ingot sizes:

1-2m long, 8cm / 15cm / 30 cm diameter

 Ingot sliced (Diamond saw)


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Silicon

Dopant: Phosphorus, N-type

Dopant: Aluminum, P-type

Active Devices: Doping pure silicon

Doping processes:

Diffusion (heat wafer in atmosphere with atoms of dopant)

Ion implantation (ions of dopant are accelerated, bombard surface)

Diode (showing doping)


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Active components: Transistors

NPN transistor

MOSFET

Metal-Oxide Silicon

Field Effect Transistor


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Active components: Integrated Circuits

Monolithic IC: Entire circuit made on a single crystal wafer

Hybrid IC: Monolithic IC + other components directly assembled into it

Hybrid micro-circuit film components


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Active components: IC’s..

Depositing films of materials on substrate to make circuits

Thin Film Processes:

Form components on circuits by vacuum evaporation, sputtering, or anodization

Film thickness is ≤ 5 mm

Thick Film Processes (silk-screening)

Print liquid or paste through a screen (mask) onto substrate  firing (baking)

Film thickness is ~ 10 mm

Silk-screening


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vacuum deposition

IC’s: Resistive elements deposition

Subtractive

process

Additive

process


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Diffused Junction Process

- Photolithography is the most

commonly used process

- Photoresists:

positive: more soluble when exposed

negative: less soluble when exposed

- Feature size = f(wavelength)

 small features need low l radiation

- Mask = = Artwork

- Projection:

- Direct: mask scale is 1:1

- Reducing: mask scale is 10:1


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Packaging of components

- Packaging puts the chip (silicon) into a protective case

- Package provides external connections that are spaced conveniently

(at distance, arranged in array) for soldering

Exploded view of TO package


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IC

Chip carrier

Packaging of components

Structure of a Surface mount component

SOIC package

Small Outline IC

Avoiding possible heat damage to IC during soldering:

- Solder a chip carrier to the PCB

- Insert chip into carrier


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[source: www.towajapan.co.jp]

Integrated Circuit (IC) Manufacture

- Slicing the Silicon ingot

- Fabrication of IC’s (Lithography, Sputtering, diffused junction, …)

- Testing each IC on the slice

- Dicing (cutting each chip out with a diamond saw)

- Packaging


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Packaging

- Make leadframe

- Die attachment (chip bonded to leadframe using epoxy)

- Wire bonding (ultrasonic welding)

- Encapsulation (moisture resistant coating)

- Molding (plastic package)

- Marking (chip number, co. name, marked on package [laser, silkscreen])

- DTFS: deflash, trim the leadframe, form the leads, singulate (cut dambars)

- Leadfinishing: electroplating the leads


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Electronics Manufacturing Processes

Manufacture of Electronics Components

Manufacture of Printed Circuit Boards (PCB’s)

Assembly of components on PCB’s


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Typical PCB

copper connections

protective covering

insulated substrate

PCB Manufacture

Types of PCB's

single-side, double-side and multi-layer

Which type to use ?

(a) Circuit complexity

(b) Available space

(c) Cost


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Manufacturing glass reinforced epoxy resin copper-clad boards

Boards are produced in "clean-rooms"

Manufacturing process: hot-pressing

• Place copper sheet on the lower plate

• Place few layers of glass cloth impregnated with epoxy on top

• [IF two-sided PCB's]: Place copper sheet on above

• Press between steel plates in a steam-heated hydraulic press (~7,000,000 Pa)

• Water cooling to 25º C

• Trim to clean out extruded epoxy

• Punch/Drill holes for alignment

• Make circuit on PCB (lithography)

• Drill through holes (for component leads)


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Multi-layer PCBs boards

• Similar process as single layer, but takes several steps

Schematics and features on

Multi-layer PCB’s


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Electronics Manufacturing Processes boards

Manufacture of Electronics Components

Manufacture of Printed Circuit Boards (PCB’s)

Assembly of components on PCB’s


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PCB Assembly boards

- Insert leaded component into holes on PCB

- Solder

- Protective coating

Manual electronics assembly

Automated electronics assembly


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Automated PCB Assembly boards

Component inputs:

Leaded Component

IC’s, components with no wire leads


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PCB Manufacture boards

Surface mount chip assembly:

- Silk-screening to apply solder paste on the board

- Automated assembly of components (>30,000 components per hour)

- IR or Wave soldering


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Land boards

Automatic soldering

Step 1. Application of the solder resist

Cover PCB with solder resist except Lands

Step 2. Flux application

Spray fluxing

Foam fluxing

Ultrasonic Spray fluxing


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Automatic soldering.. boards

Step 3. Solder Application

Dual wave solder bath


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Automatic soldering.. boards

Step 4. Automatic removal of solder bridges: Hot air-jet knives



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Special considerations boards

for SMT boards


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